This invention relates to a steering angle sensor, which is equipped for installation in a steering arrangement of a motor vehicle.
Such steering angle sensor comprises a rotatably mounted (about a first axis) first gearwheel which upon actuation of the steering arrangement rotates about its axis, and at least one rotatably mounted (about a further axis) second gearwheel which is in engagement with the first gearwheel and which thereby is carried along with a rotary movement of the first gearwheel, so that it rotates about its own axis and with reference to the rotary movement of the second gearwheel a steering angle of the steering arrangement can be determined.
The steering arrangement in particular can be a steering arrangement which includes a steering wheel rotatably mounted about a steering axle. While a steering wheel is turned by a driver, a torque is introduced into a steering gear associated to the steering wheel, which triggers a rotary movement at components of the steering gear. A steering angle representative for such steering arrangement can relate both to the steering wheel itself and to a component of the steering gear associated to the steering wheel. Furthermore, an operating element other than a steering wheel also can be used for generating a corresponding torque and a steering angle connected therewith.
A known steering angle sensor of the type mentioned above comprises a transmission with a rotatably mounted central gearwheel and two satellite gearwheels in engagement therewith, wherein the central gearwheel is rotated upon actuation of the associated steering arrangement and thereby carries along the two satellite gearwheels. On each of the satellite gearwheels a magnet, e.g. a permanent magnet, is arranged, whose magnetic field changes its spatial orientation during a rotary movement of the corresponding satellite gearwheel. This can be detected by a detector associated to the respective satellite gearwheel, from which in turn a steering angle of the associated steering arrangement can be determined, cf. WO 96/27116 A1.
By using two satellite gearwheels with different size and/or different tooth numbers different gear ratios can be achieved when the respective satellite gearwheel interacts with the central gearwheel. By the combined determination of the change of the magnetic field on both satellite gearwheels, it then is possible to not only determine changes of the steering angle, but also absolute values of the steering angle.
The accuracy in the detection of the steering angle among other things depends on the quality of the engagement between the gearwheels of the steering angle sensor. In particular, a clearance between the toothings in engagement with each other can lead to inaccuracies in the determination of the steering angle.